The invention deals with a procedure and structure for the processing of short messages under phone number portability in cellular phone systems.
Short messages (SM) as defined in this invention are not limited to SMS (Short Message Service) and/or MMS (Multimedia Messaging Service).
The introduction of phone number portability in cellular phone service, also called mobile number portability (MNP), which also covers the Short Message Service, was required by the regulating authority for telecommunication and postal service (RegTP); this portability is described in principle in ETSI EN 301 716 (GSM 03.66). Based on the experience in actual operation, it is now known that normally several attempts are necessary to deliver an MT-SM (Mobile Terminated Short Message), i.e. a short message (SM) intended for delivery to a mobile terminal. This requires so-called retries, which are in principle identical in procedure to the initial delivery attempt of an MT-SM. However, GSM 03.66 describes generally only the first delivery attempt, but not the additional retries that are normally required. Given the fact that the introduction of MNP has the result that the international cellular user phone number (MSISDN) of a recipient of an MT-SM provides no information regarding the current subscription network; because the user may transfer the MSISDN into a different cellular network (PLMN), the interrogating network must now always request user data first from the subscription network. Prior to delivery of a SM waiting in a SMS center (SMSC), it now needs to retrieve the address of the “visited MSC”, i.e. the transfer node of the cellular network currently used by the recipient, from the home register (HLR) of the subscription network and the international cellular user identification (IMSI) of the recipient. This is handled by various procedures that vary in complexity, but that will eventually yield the needed information, such that it is available after all. The sending entity, which is the HLR in the subscription network of the recipient, also sends his calling party address (CgPty address) as the sender's address. However, this is deleted after each delivery attempt of the SM in all currently known procedures. Thus, the SMSC must address the intended HLR again via a so-called MNP-SRF network element (Mobile Number Portability Signaling Relay Function) for each subsequent retry, even in those cases where the HLR is in the own PLMN. This procedure has been used to-date prior to MNP and continues to be used after MNP essentially unchanged, which leads to the inefficiency described above.
It is thus the objective of the invention to describe a procedure for the processing of short messages under phone number portability in cellular networks, where the load on the network elements involved is reduced and the delivery of short messages is accelerated. A structure to handle the procedure is also described.
The objective is solved in the invention by the characteristics of the independent patent claims.
Advantageous embodiments and further improvements of the invention are described in the dependant patent claims.